A prior art ring laser gyroscope is described in U.S. Pat. No. 4,344,706, issued Aug. 17, 1982 and U.S. Pat. No. 4,473,297, issued Sept. 25, 1984. The prior art gyroscope comprises a triangular block which has a triangular cavity for both a clockwise beam and a counterclockwise beam, a pair of anodes and a cathode for energizing the beams, three mirrors respectively located at the three corners of the block, a beam combiner assembly for measuring the gyroscope output, and means to minimize beam lock-in.
A problem with the prior art gyroscope is that the means to minimize lock-in is not sufficiently effective for some installations. The lock-in is a region of angular rate input around zero input rate in which the two oppositely directed traveling waves or beams are synchronously locked due to mutual coupling therebetween.